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Published on: April 22, 2016
Biosynthesis of pullulan using immobilized Aureobasidium pullulans cells.
A Mulchandani1, J H Luong, A LeDuy
1Biotechnology Research Institute, National Research Council of Canada, Montréal, Québec, Canada.
Biotechnology and Bioengineering
|January 15, 1989
Summary
Immobilizing Aureobasidium pullulans in polyurethane foam enhances shear resistance for repeated pullulan biosynthesis. Adsorption methods were less effective for stable cell immobilization and product yield.
Area of Science:
- Biotechnology
- Microbial Immobilization
- Biopolymer Production
Background:
- Aureobasidium pullulans is a yeast capable of producing pullulan, a valuable exopolysaccharide.
- Efficient immobilization of microbial cells is crucial for industrial bioprocesses, improving stability and reusability.
- Previous methods for A. pullulans immobilization have limitations in terms of cell loading, stability, or reusability.
Purpose of the Study:
- To investigate and compare two immobilization techniques for Aureobasidium pullulans: adsorption onto solid supports and entrapment within polyurethane foam.
- To evaluate the impact of immobilization methods on cell loading, pullulan biosynthesis, and cell stability.
- To determine the optimal conditions for cell immobilization and assess the reusability of immobilized cells for pullulan production.
Main Methods:
- Immobilization of Aureobasidium pullulans via adsorption on solid supports and entrapment in open-pore polyurethane foam.
- Optimization of adsorption conditions, including pH and surface modifications (cationic coatings).
- Fermentation experiments to assess pullulan yield, cell leakage, and shear resistance of immobilized cells.
Main Results:
- Adsorption yielded a maximum cell loading of 0.012-0.018 g dry wt/cm(2) at pH 2.0, a condition that inhibited pullulan synthesis.
- Cationic coatings did not significantly improve cell-support binding strength.
- Both surface-immobilized and polyurethane foam-entrapped cells produced approximately 18 g/L pullulan, with about 5 g/L leaked cells.
- Polyurethane foam-entrapped cells demonstrated superior shear resistance compared to surface-immobilized cells.
Conclusions:
- Entrapment in open-pore polyurethane foam is a more effective method for immobilizing Aureobasidium pullulans due to enhanced shear resistance.
- Immobilized Aureobasidium pullulans, particularly when entrapped in polyurethane foam, can be repeatedly used for pullulan biosynthesis.
- Further research may focus on optimizing polyurethane foam entrapment for higher cell density and improved pullulan yield.
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